1. Field of the Invention
The present invention relates to a resist stripping method and a resist stripping apparatus for stripping away an unnecessary resist from surfaces of various types of substrates such as a semiconductor wafer, a glass substrate for a liquid crystal display device, a glass substrate for a plasma display, a substrate for an optical disk, a substrate for a magnetic disk, a substrate for a magneto-optical disk, and a substrate for a photomask.
2. Description of Related Art
In the steps of fabricating semiconductor devices and liquid crystal display devices, processing (resist stripping processing) for stripping an unnecessary resist from surfaces of substrates such as semiconductor wafers and glass substrates for liquid crystal display panels, for example, is performed. As types of the resist stripping processing, batch processing for collectively processing a plurality of substrates has conventionally prevailed. However, in recent years, as the substrate to be processed increases in size, single substrate processing for processing substrates one at a time by supplying a resist stripping liquid to a surface of the substrate has been paid attention to.
A conventional single substrate processing apparatus for performing resist stripping processing comprises a spin chuck for holding and rotating a substrate almost horizontally and a nozzle for supplying a resist stripping liquid to a surface (an upper surface) of the substrate held by the spin chuck. In the resist stripping processing, while the substrate is being rotated at a rotational speed of approximately 10 rpm by the spin chuck, the resist stripping liquid is supplied from the nozzle to the vicinity of the rotation center on a surface of the substrate which is being rotated. The resist stripping liquid supplied to the surface of the substrate receives a centrifugal force produced by the rotation of the substrate, to flow while being enlarged toward a peripheral edge of the substrate from the vicinity of the rotation center which is the position where the resist stripping liquid is supplied. Thus, the resist stripping liquid spreads over the entire area on the surface of the substrate, so that the resist stripping processing for the surface of the substrate is achieved.
Since the rotational speed of the substrate at the time of supplying the resist stripping liquid is low, however, it takes time for the resist stripping liquid to spread over the entire area on the surface of the substrate and it takes long to require the resist stripping processing (processing throughput is low).
Since the resist stripping liquid supplied to the center on the surface of the substrate flows while reacting with a resist on the surface of the substrate, the processing capability is gradually degraded until it reaches a peripheral portion of the substrate. The resist at the peripheral portion on the surface of the substrate is not patterned and is formed in a thick film state. In the resist stripping liquid whose processing capability is degraded, therefore, the resist at the peripheral portion of the substrate cannot be completely stripped.